US2382621A - Process of making battery separators - Google Patents

Description

Aug. i4, 1945` E. FAIRCLOUGH PROCESS OF MAKING BATTERY SEPARATORS Filed July 51,'1942 frumres by Pressure or Sua for? Press/fly ad fyi/zy l'n fz steam #en fed fuss IN VEN TOR.

Patented Aug. 14, 1945 raocsss or MAKING BATTERY ssrarmrms Edward Fairclough, Cleveland, Ohio, assigner to Willard Storage Battery Company, Cleveland, (Ehio, a corporation oi' West Virginia Applieation July 31, 1942, Serial No. 453,087

7 Claims.

The invention may be further briefly sum marized as consisting in certain novel steps of procedure hereinafter described and particularly set out in the appended claims.

This application is in part a continuation of my earlier application Serial No. :fiilz ed August i, wel, and' now Patent No. 2,314,203 v* issued March it, w43.

In the accompanying sheet of drawings,

Fig. 1 is a perspective View partly in section showing a, storage battery separator made oi' rmatted tree bart. fibers and produced by my novel process; and

Fig. 2 is, a view more or less diagrammatic in torno end'indicating process steps for producing battery separators or the like according to my invention.

in Fig. l I show a separator l@ for use between the adjacent positive and negative plates of a storage battery and which is in the form of a sheet made of matted tree bari: fibers. The separator may be of size and thickness suitable for the battery in which the separator is to be used. in making the separator i@ I prefer to use bark ibers obtained from trees of the' Sequoia group such as the redwood trees because the fibers obtained from the bark of these trees are suiiciently long to secure satisfactory matting or felting and possess other desirable characteristics, but i may use bers obtained from the bark of various other trees if ,the iibers are of suitable length. Redwood bark iibers also have a crinlrly character which materially aids in matting or felting these fibers.

In forming the separator the bers are matted together and pressed into a sheet, and although the bers do have sumcient ,adhesive qualities to permit such separators to be successfully produced without the use of a binder, i prefer to use a binder to aid in keeping the fibers from falling apart. Any suitable substance may be used as a binder such as latex, hard rubber dust, or asphalt. I find that a variety of natural asphalt known as gilsonite," which is found in the' Uinta Valley, Utah, and occurs generally as rounded masses oi.' brilliant black solid hydrocarbon, forms a. very satisfactory binder. Ia'lso (Cl. 13G-150) providing they are acid resistant and do not introduce any undesirable matter into the electrolyte solution. One such resin is a pine resin known commercially as VinsoL Suitable synthetic resins could also be used such as styrene and vinylydene chloride. When a binder, of the kind 'already mentioned, is employed it should be used in a relatively small amount so as not to interfere with or detract from the absorbent qualities of the separator.

In some instances it may be desirable to add jute bers or other vegetable or mineral iibers to the tree bark fibers, instead of one of the abovementioned binders, to give vthe separators.

initial strength so that they can be handled satisiactorily. l may also'cary out certain steps of my process with the fiber mat disposed between sheets of par which give 'added strength to the mat and facilitate the handling thereof. I

These sheets of paper may be peeled or stripped from the mat or finished separator at the desired time, preferably just before the separator is to be placed in the battery, although in some cases the paper sheets may be left on the separator so' as to be incorporated in the battery in. which the separator is placed.

I have found the fibers obtained from the bark of redwood trees to be especially suitable for making battery separators because they are suflciently long fibers which will form a good mat without the use of any binder whatever, particularly after the caustic treatment hereinafter described, and will form an excellent mat with only a limited amount of binder. The redwood bark .berssalso have aV high lignin content which not only adds to the life of the separator and makes t Another desirable characteristic of the redwood bark fibers is that they do not hydrolyze appro ciably in acid. Various materials, particularly cellulose, tend to lose their strength and resiliency in acid, but redwood bark bers contain a relatively snjiall amount of cellulose and probably for this reason possess the quality of resisting ily-f nd that certain resins make satisfactory binders 55 dlfOlYSviS- I als@ nd thatfbattery separators made from redwood bark bers have a satisfactory low electrical resistance. s

In making storage battery separators from redwoodbark or other suitable tree bark, the bark is stripped from the tree, chopped into pieces of convenient size, and passed through a shredding apparatus which liberates the fibers. The shredded material is cleaned as by screening or any other suitable operation to separate the fibers from the dustl dirt, and other matter. The shredding and separation of the fibers from the other matter are preferably carried out with the material in a dry or natural state. The bark fibers thus obtained are'relativelyv long and more or less round and crinkly in form.

The bark fibers are then subjected to a treatment in a caustic solution which removes various impurities such as resins, miscellaneous organic material, small amounts of manganese, and various other ingredients that would prove harmful to storage battery plates. In carrying outthis treatment, the bark fibers may be placed in a filter vessel or container, which may be cheesecloth .ind which retains the fibers and permits the'treating liquid to circulate through the mass. While the fibers are retained in the filter vessel or Vcontainer they are subjected to cooking in a treatment apparently removes very little, if any Vof the cellulose from the fibers, although the treatment may reduce the weight of the fibers by.

approximately 25% or 30%.

fsatisfactory battery separator, I mix together 'I'he washed fibers are next placed in a mixer\ 40 together with a wetting or foaming agent Yand the desired binding material, if one is to be used. The fibers may be dried before being placed in the mixer or-may be pl'aced therein in the wetcondition in which they come fromthe washing operation following the caustic treatment. The foaming agent should be a substance which will wet the fibers individually and will also produce a foam so that the fibers willseparate or be held apart and willnot remain in lumps or clots. Although various substances can be used for this purpose, those compounds or salts chemically known as neutral soaps or detergents, and also known as foam producing wetting agents, are preferred. vThis foaming agent or so-called "soap solution" is preferablya 1% solution although this value may be increased or decreased somewhat as circumstances may require. As the above mentioned foaming and wetting agent any one of a large group of available substances of this kind can be used. As being representative of this class, the following substances or preparations can bementioned: soap bark; Acquerex which consists of sodium salts of sulphate mon-esters of a mixture of higher fatty alcohols; Nacconol" which is the trade name for what is believed to be alkyl aryl sulphonate; Saponin which is an extract ofthe bark of `Quillaia, root or Indian chestnut; "Tergitol penetrant which is a sodium salt of higher secondary alkyl sulfate; Aerosol" which is an alkyl aryl sulfonate;

"Orvus" which is a fatty alcohol sulfate; "Dreft which is also a fatty alcohol sulfate; "Aresklene" which is dibutyl phenyl phenol sodium disulfonate; Santomerse. which `is alkylated aryl sulionate; Nekal A which is sodium alkyl naphthal'ene sulfonate; and Daconol" which is alkyl aryl sodium sulfonate.

As stated above, the binderis also placed in the mixer and during the mixing operation the binder becomes thoroughly distributed among the fibers. The binder should be either in a powdered or granular form. and the grains or particles should not be of a larger size than that corresponding with a 35 mesh screen and should not be finer than mesh. Instead of a powfiered or granular binder, I can use certain, synthetic resins in thread or filament form. Any one of the binders above mentioned may be used. but I prefer to use the natural asphalt known as gilsonite which is insoluble in water. The amount of binder to be used should be relatively small, as mentioned above, so as not to decrease the absorbent properties of the matted fibers. I nd that the use of 10% to 20% by weight of the binder gives good results although the amount used can be varied somewhat and can be more or less than the percentage mentioned.

The mixing operation need be continued only a few minutes, but the mixing period will depend on the speed of the mixer, its size, and the amount and character of the material being treated, as well as various other factors. The temperature of the foaming agent or soap solution will also affect the period of mixing because a` higher temperature will increase the speed at which the foam isv produced during the mixing.

As an example of the mix employed in my process and from which I have obtained a very 3% pounds of the tree bark fiber, 14 pounds of water, 209 grams of gilsonite, and 340 cc. of 10% solution of the foaming agent. This amount of a 10% solution of the foaming agent when mixed with the 14 pounds of water produces approximately 1/% Solution, by weight, of the foaming agent.

A general formula based on the weight of the total mix may be stated as follows: Fil/2% fiber, 21/2% gilsonite, and 80% water, the latter being a 1/2% solution of the foaming agent.

'I'he amounts of the ingredients specified in the above vexample and formula can be varied and can be` greateror less than stated. depending upon the characteristics of the fiber', the kind of foaming agent employed, and various other factors. A

From 181/2 pounds of theabove-specitled mix I find that I can produce 10 sheets or separators having a total area of approximately 16 square feet with a thickness of about .095 and a density of .23 pounds per square foot. l

Following the treatment of the tree bark fibers in the mixer, the foaming agent or soap solution is removed from the fibers. 'I'his may be accomplished in part by placing a mat or layer of the fibrous material on a screen through which the liquid may drain. Most of the liquid remaining in the brous material may then be removed by subjecting the material to a squeezmg operation in a suitable press. Instead of this squeezing operation, suction can be applied to the material while supported on the screen `to draw the liquid therefrom. A

After the removal of the foaming agent or soap' assasai 3 l The thickness of the sheet into which the matted material 24 is compressed or molded may be de-..` termined kby the height or thickness of a suit z`a.ble-k mold or mold ring 28 in which the material -is by a screen. The wash water is removed from the mat' or layer either by the application of pressure or suction as explained above in the removal of the foaming agent orsoap solution. The step of washing the brous material can be' omitted if desired.

' The mat or layer remaining after the removal lof the foaming agent or soap solution (or the removal of the wash water) is still damp or wet `and is next subjected to a drying and molding operation. At this time the damp mat can be y placed, between two sheets of paper, although thel use of paper is not necessary and can be omitted if desired. The mat, with or without the paper "sheets, is then transferredto a press, such as the press 20 shown in Fig. 2, in which itis subjected to heat and pressure. Instead of ,placing the mat immediately in the press 20, it can, if desired, be

placed on a hot plate while waiting for the pressing operation and during this interval of time some of the liquid would be evaporated from the material so as to shorten the time required for the pressing operation. Instead of using a press,

` the material might also Ibe subjected to pressure between heated rolls.` The pressure which is applied to the material compresses or molds the same into a' sheet of a thickness suitable for battery separators. The heat which is applied to the material serves to dry the same by evaporating the moisture therefrom and also serves to soften the binder so that it will adhere to the fibers and hold them together. The gilsonite or natural asphalt which I have mentioned above asY being la satisfactory binder has a relatively high melting point and thus permits a relatively high temper ature to be used in the press which expedites the drying of the material. The temperature at which the material is heated should preferably be lust below the melting point of the binder so that the binder will be softened but will not actually iiow. I iind that a temperature in the neighplaced.

The sheet obtained from the pressingand drv-` ing operation is then trimmed to the size and shape desired for the battery separator I0 and the ber trimmings resulting from this operatic are salvaged and returned to the mixer.`

u From the foregoing description and accompanying drawing it willbe readily understood that I have provided a novel process by which storage battery separators can be economically produced from wood bark fibers, such as the fibers vof redwood bark which has heretofore been reical solution, and pressing the fibrousi mixture into a sheet.

2. Theprocess oi making battery separatorst which comprises treating tree bark bers with caustic solution, removing the caustic ,solution from the bers, adding tothe fibers a binder and awetting and foam producing chemical solution, -agitating the fibers and binder while in said wetting and foam producing chemical solutionl so as to distribute the binder and'produce foam for holding the fibers apart, arranging the brous mixture to form a mat and removing the lastborhood of 335 or 340 F. is .very satisfactory Iin the pressing and `drying operation when gilsonite is used as the binder but this temperature may be increased er decreased with the use of different binders and as different conditions may require.

So far as I am aware, the feature of incorporating a binder in granulan or powdered form in a mass oi' bers and pressing or molding the mass -while heated to a temperature which is below the melting point of the binder but which softens the binder to secure adhesion of the bers, is broadly fill new and is applicable to the manufacture :if various products other than storage batterysepara any suitable construction such as that shown inv Fig. 2. As here illustrated, the press may comprise stationary and movable platens d@ and 23 between which a layer or mat 2d of the material is received. Steam or other suitable heating agent may be supplied to the platehs by conduits 22a and 23a. A cylinder 25 incorporated in the base of the press is provided with a piston which is connected with the movable platen 23 by the piston rod 26 so that when the piston is actuated hydraulically or otherwise, the platens will subject the material to a desired pressure which may be in the neighborhood of 500 lbs. per square inch.

mentioned solution therefrom. andl subjecting the mat to heat and pressure to form a sheet. a 3.l The process of making battery separators which comprises treating tree bark bers with caustic solution, removing the caustic solution from the zers, adding to the bers a binder and a wetting and foam producing chemical solution,

agitating the bers and binder while in said wetting 4and foam producing chemical solution so as to distribute the binder and produce foam for holding the fibers apart. removing said last-mentioned solution, and subjecting the treated bers to heat and pressure to dry the same and press,

them into a sheet.

4. The process of making battery separators which comprises treating tree bark ii'bers with caustic solution, washing the fibers to remove the caustic solution, adding to the bers a wetting and foam producing chemical solution and a binder in granular or lament form, agitating the fibers and binder while in the last-mentioned solution se as to distribute the binder and produce foam for holding the fibers apart, removing said last-mentioned solution, and drying the treated iibers and pressing them into a sheet by applying heat and pressure'thereto.

5. The process of making battery separators which comprises treating tree bark bers with caustic solution, washing `the fibers te` remove the caustic solution, adding to the vlbers a wetting and foam' producing chemical solution and a binder in granular or lament iorm, agitating the bers and binder while in the last-mentioned solution so as to distribute the binder and preduce'ioam for holding the bers apart. squeezing the resulting iibrous mixture for removing said last-mentioned solution therefrom, 'and drying the mixture and pressing it into a sheet by applying heat and pressure thereto. t

6. The process of making battery separators which comprises treating tree bark fibers with caustic solution, removing the caustic solution, adding to the fibers a binder and a; wetting and foam producing chemical solution, agitating the fibers and binder while in said wetting and foam producing chemical solution so as to distribute fthe binder and produce foam for holding the bers apart, arranging the resulting fibrous mixture to form a, niet and removing the last-mentioned solution, placingthe mat between sheets

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